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Editorial Team
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Asked: 2026-05-22T17:45:49+00:00

Anyone know why this won’t compile? The problem has to do with inheriting from

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Anyone know why this won’t compile? The problem has to do with inheriting from the Workflow Activity. 

public class MyActivityBase<T> : System.Workflow.ComponentModel.Activity
{
    public T MyProperty { get; set; }
}

Compile Error Message

Error   1   Could not create activity of type '...Activities.Common.MyActivityBase`1'. System.ArgumentException: Cannot create an instance of ...Activities.Common.MyActivityBase`1[T] because Type.**ContainsGenericParameters is true**.
   at System.RuntimeType.CreateInstanceCheckThis()
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Workflow.ComponentModel.Compiler.XomlCompilerHelper.InternalCompileFromDomBatch(String[] files, String[] codeFiles, WorkflowCompilerParameters parameters, WorkflowCompilerResults results, String localAssemblyPath)

Thanks,
T

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1 Answer

  1. Editorial Team

    Your type is being instantiated via Reflection. Whatever code is doing the instantiation doesn’t know how to instantiate a type with Generic parameters. It therefore throws an Exception.

    Unfortunately, there’s really nothing you can do if you want to use MyActivityBase<T> directly. You might be able to get by using concrete child implementations of your base class though (something like public class MyActivityString : MyActivityBase<string>)

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